1. Field of the Invention
The present invention relates to a lifting mechanism for a head member of a pipe bender, and more particularly a lifting mechanism for a head member of a pipe bender, which can make the head member move up and down smoothly, and eliminate the risk of undesirable downward movement of the head member caused by oil leakage or other breakdowns of the hydraulic cylinder.
2. Brief Description of the Prior Art
Referring to FIGS. 7 and 8, a conventional pipe bender includes a head member 10, a molding member 20, a foldable hand member 30, and a feeding element 40. The head member 10 is tip and down movably disposed at a front end of the pipe bender. The molding member 20, and the foldable hand member 30 are fitted to the head member 10. Ad, the feeding member 40 is fitted on the main body of the pipe bender for feeding pipes to the head member 10.
The head member 10 is equipped with a rear guide block 101, a rear guide mould 102, a guide block 103, and a guide mould 104. The molding member 20 consists of several decks of molding wheels 201 of different diameters. The foldable hand member 30 includes an upper clipping element 301, and a lower clipping element 302 arranged beside corresponding molding wheels 201.
In using such pipe bender, pipes fed to the head member 10 via the guide moulds 102, 104 on the head member 10 are clipped by means of one of the clipping elements 301, and 302. Then, the clipping element 301 or 302 operate to press the pipes over the corresponding molding wheel 201 so that the pipes are bent in conformity with shapes and diameters of the molding wheel 201.
Referring to FIGS. 9 and 10, the head member 10 is fitted to vertical guide rails at one side, and equipped with a lifting mechanism 50 comprising a hydraulic cylinder 501, which is disposed under the head member 10 with a piston rod 502 propping the bottom of the head member 10. Thus, the lifting mechanism 50 can be operated to adjust the height of the head member 10. After the head member 10 is adjusted to a desired height, pipes fed from the feeding member 40 can be clipped by one of the clipping elements 301, 302 that is as high as it, and then shaped in accordance with the corresponding molding wheel 201 when the clipping element is operated.
However, the lifting mechanism for head member is found to have disadvantages as followings:
1. The entire weight of the head member 10 is supported by the cylinder 501 therefore the lifting mechanism will have shortened service life. And, the head member will undesirably move down due to gravity if there is breakdown in the cylinder or leakage in the oil circuit.
2. The head member 10 is prone to vibrate because it is relatively heavy in weight. Consequently, the head member 10 will have reduced precision.
3. Because the hydraulic cylinder 501 of the lifting mechanism is disposed under the head member 10, it is likely to interfere with bending process of pipe benders.
It is a main object of the present invention to provide a lifting mechanism for a head member of a pipe bender such that the head member can be moved up and down smoothly.
It is another object of the present invention to provide a lifting mechanism for a head member of a pipe bender such that an oil cylinder thereof do not have to bear the weight of the head member after the head member has been moved to desired position, eliminating the risk of undesirable downward movement of the head member caused by oil leakage or other breakdowns of the hydraulic cylinder.
The present lifting mechanism includes a connecting block, and an oil cylinder. The connecting block is joined to the head member. The oil cylinder is horizontally fitted to the main body of the pipe bender. The connecting block is equipped with a propped block on the bottom. The propped block has several horizontal propped surfaces on the bottom, which are formed at different heights with slopes formed in between. Wheels are fitted to the piston rod of the cylinder to prop up the propped block. Therefore, when the cylinder operates for the wheels to move relative to the propped block, the head member can be moved up and down. The piston rod stops moving when the wheels are positioned under one of the horizontal propped surfaces, therefore the cylinder don""t have to bear the weight of the head member all the time.